There are numerous instances in which it is desirable to introduce air into a liquid. Among such instances are aerobic digestion, activated sludge, lagoons and ponds, oxidation pools, sewage treatment plants, minnow tanks, bacteria culture laboratories, and so forth. Numerous means have been devised for introducing air into a liquid. Often, such means has taken the form of some device which circulates the liquid and in the process introduces air. For example, water may be pumped downwardly through a tube with the air being drawn in as a result of the movement of the liquid. In some cases, the liquid is simply thrown up into the air entraining air as it falls. Many of these prior art devices rely upon movement of the liquid in order to create the necessary movement of the air. Consequently, additional power is required since the movement of a liquid requires greater effort than the movement of air alone.